JP2016148749A - Dispersion shifted optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion shifted optical fiber in which variance in light loss due to bending of the optical fiber can be suppressed.SOLUTION: In a dispersion shifted optical fiber DSF1 which propagates light of a C band and an L band, a first center segment 10 has a radius r0 of 0.3-2.8 μm, and a relative index difference Δ0 of 0.4-0.9%. A first segment 11 has a radius rof 1.8-5.0 μm. A second segment 12 has a radius rof 5.0-8.0 μm, and a relative index difference Δ2 of -0.02-0.07%. A third segment 13 has a radius rof 6.0-8.5 μm, and a relative index difference Δ3 of 0.285-0.5%. A fourth segment 14 has a radius rof 0.0-16.0 μm, and a relative index difference Δ4 of -0.02-0.04%. Here, r≤r<r<r<rholds.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a dispersion-shifted optical fiber and is suitable for suppressing variation in bending loss of light propagating through a core.

  Single mode optical fibers are used in optical communication transmission networks. As an optical communication using this single mode optical fiber, wavelength division multiplexing (WDM transmission) is widely accepted. Wavelength multiplexing transmission is a system for transmitting a plurality of optical signals using a plurality of wavelengths instead of a single wavelength for optical communication, and is an optical transmission system suitable for high-capacity high-speed communication.

  In WDM transmission, a dispersion-shifted optical fiber is sometimes used to suppress chromatic dispersion. In particular, a non-zero dispersion-shifted optical fiber (Non-Zero Dispersion Shifted fiber) that suppresses dispersion due to the wavelength of light and does not make the dispersion zero. Fiber: NZDSF) may be used.

  Patent Document 1 below describes a dispersion-shifted optical fiber. In the dispersion-shifted optical fiber described in Patent Document 1 below, the core has three segments.

Japanese Patent No. 4393708

  However, in the dispersion-shifted optical fiber described in Patent Document 1, so-called bending loss, in which light propagating when the dispersion-shifted optical fiber is bent, varies when the ratio of the cladding diameter to the core diameter changes. I found it easy. A general optical fiber preform includes a core composed of a rod-shaped core glass body serving as a core, and an inner peripheral cladding glass body that covers the outer peripheral surface of the core glass body and serves as an inner peripheral portion of the cladding. It is produced using a coated rod. Then, by using a jacket method or an OVD method (Outside vapor deposition method), the outer peripheral surface of the core-covered rod (on the outer peripheral surface of the inner peripheral clad glass body) is covered with the outer peripheral clad glass body which is the outer peripheral side of the clad. . In general, since the outer clad glass body is often manufactured at low cost, the outer diameter of the outer clad glass body is likely to fluctuate. Thus, the fact that the outer diameter of the outer clad glass body varies leads to the fluctuation of the outer diameter of the optical fiber preform. On the other hand, the clad diameter of an optical fiber manufactured by drawing an optical fiber preform is constant, for example, 125 μm. For this reason, when the outer diameter of the optical fiber preform changes, the ratio between the cladding diameter and the core diameter changes. As described above, there is a concern that the variation in the bending loss of the light propagating through the dispersion-shifted optical fiber to be manufactured increases due to the change in the ratio of the core diameter to the cladding diameter as described above due to the manufacturing error. The optical fiber may be laid in a bent state as well as when laid in a straight line. Therefore, it is not preferable that the bending loss of the propagating light varies as described above.

  Therefore, an object of the present invention is to provide a dispersion-shifted optical fiber that can suppress a change in bending loss even when the ratio between the core diameter and the cladding diameter changes.

In order to solve the above problems, the present invention provides a dispersion slope in light having a wavelength of 1530 nm or more and 1625 nm or less and a dispersion value in light having a wavelength of 1550 nm of 2.0 ps / nm / km or more and 13.5 ps / nm / km or less. There is a 0.092ps / ^nm 2 / km or less, the cable cutoff wavelength is less 1450 nm, the effective core area in the light of the wavelength of 1550nm is at 65 .mu.m ² or more 90 [mu] m ² or less, the mode of light having a wavelength of 1550nm A dispersion shifted optical fiber having a field diameter of 9.2 μm or more and 10.5 μm or less, characterized by the following.

  The core includes a first segment including a central axis of the core, a second segment surrounding the outer peripheral surface of the first segment without a gap, a third segment surrounding the outer peripheral surface of the second segment without a gap, and the third segment A fourth segment surrounding the outer peripheral surface of the segment without a gap, and the first segment includes a first central segment including the central axis.

Further, the radius r ₀ of the first central segment is 0.5 μm or more and 2.8 μm or less, the radius r ₁ of the first segment is 1.8 μm or more and 4.5 μm or less, and the radius r of the second segment is ₂ is 4.0 μm or more and 8.0 μm or less, the radius r ₃ of the third segment is 4.5 μm or more and 8.5 μm or less, and the radius r ₄ of the fourth segment is 8.0 μm or more and 16.0 μm or less. And r ₀ ≦ r ₁ <r ₂ <r ₃ <r ₄ holds.

Furthermore, the relative refractive index difference Δ _{0 with} respect to the cladding surrounding the core of the first central segment is 0.4% or more and 0.9% or less, and the relative refractive index difference Δ _{2 with} respect to the cladding of the second segment is is 0.00% or more less than 0.07%, the relative refractive index difference delta ₃ with respect to the cladding of the third segment is less than 0.5% 0.285%, the ratio with respect to the cladding of the fourth segment the refractive index difference delta ₄ is 0.04% or less than 0.005%, in the first segment relative refractive index difference with respect to the cladding is lowered toward the inner periphery of the second segment from the outer periphery of said first central segment .

  As a result of intensive studies, the present inventors have found that the ratio of the core diameter to the cladding diameter changes according to the dispersion-shifted optical fiber characterized by the above, that is, the dispersion-shifted optical fiber that propagates C-band and L-band light. Even in this case, it was found that the bending loss of light propagating through the core is difficult to change. Therefore, according to the dispersion-shifted optical fiber of the present invention, variation in characteristics can be suppressed even when the refractive index of the cladding varies due to manufacturing.

Further, in the above-described dispersion-shifted optical fiber, the radius r ₀ of the first central segment and the radius r ₁ of the first segment may be configured to match. In this case, the radius r ₀ of the first central segment is 1.8 μm or more, the radius r ₁ of the first segment is 2.8 μm or less, and the radius r ₂ of the second segment is 5.0 μm or more 6 0.6 μm or less, the radius r ₃ of the third segment is 6.1 μm or more, the relative refractive index difference Δ ₀ of the first central segment with respect to the cladding is 0.8% or less, and the second segment the relative refractive index difference delta ₂ with respect to the cladding is preferably set to 0.06% or less.

Since the radius r ₀ of the first central segment and the radius r ₁ of the first segment is matched, the first segment and thus be composed of substantially the first central segment. That is, the first segment has a step-type refractive index distribution, and the relative refractive index difference with respect to the cladding is the relative refractive index difference Δ _{0 of} the first central segment. Since the first segment has a step-type refractive index distribution in this manner, the manufacturing becomes easier than when the refractive index is changed in the first segment.

When the first segment has a step-type refractive index distribution as described above, the radius r ₀ of the first center segment is set to 2.0 μm or more and 2.6 μm or less, and the radius r ₂ of the second segment is set to 6.0 μm or less, the radius r ₃ of the third segment is 7.5 μm or less, the radius r ₄ of the fourth segment is 11.0 μm or more and 15.0 μm or less, The relative refractive index difference Δ _{0 with} respect to the cladding is 0.47% or more and 0.67% or less, the relative refractive index difference Δ _{2 with} respect to the cladding of the second segment is 0.02% or more, and the third segment the relative refractive index difference delta ₃ relative to the cladding is less 0.35%, the relative refractive index difference delta ₄ with respect to the cladding of said fourth segment is to be 0.025% or less than 0.010% More preferable.

  By having such a refractive index distribution, even when the ratio between the core diameter and the cladding diameter changes, the change in bending loss of light propagating through the core can be further suppressed.

Alternatively, in the dispersion shifted optical fiber, the radius r ₀ of the first center segment may be configured to be smaller than the radius r ₁ of the first segment. In this case, the radius r ₀ of the first central segment is 1.3 μm or less, the radius r ₁ of the first segment is 2.0 μm or more, and the radius r ₂ of the second segment is 5.0 μm or more. The radius r ₃ of the third segment is 6.0 μm or more, the radius r ₄ of the fourth segment is 9.0 μm or more, and the relative refractive index difference Δ ₀ of the first center segment with respect to the cladding is It is preferably 0.5% or more.

As described above, in the dispersion-shifted optical fiber of the present invention, in the first segment, the relative refractive index difference with respect to the cladding decreases from the outer periphery of the first central segment to the inner periphery of the second segment. Therefore, the radius r ₀ of the first central segment is configured to be smaller than the radius r _{1 of} the first segment, so that the first segment has a substantially trapezoidal refractive index distribution. Since the first segment has a substantially trapezoidal refractive index distribution in this way, it is possible to gradually change the viscosity difference in the region from the outer periphery of the first central segment to the second segment in the first segment. . For this reason, a large residual stress can be reduced and an increase in transmission loss can be suppressed.

When the first segment has a trapezoidal refractive index profile as described above, the radius r ₀ of the first center segment is 0.5 μm or more and 1.0 μm or less, and the radius r ₁ of the first segment is The radius r ₂ of the second segment is not less than 5.2 μm and not more than 6.5 μm, and the radius r ₃ of the third segment is not less than 6.5 μm and not more than 8.0 μm. The radius r ₄ of the fourth segment is 10.0 μm or more and 13.5 μm or less, and the relative refractive index difference Δ _{0 with} respect to the cladding surrounding the core of the first central segment is 0.6% or more and 0.8% or less. The relative refractive index difference Δ ₂ of the second segment with respect to the cladding is 0.020% or more and 0.065% or less, and the relative refractive index difference Δ ₃ of the third segment with respect to the cladding is 0.4%. And It is a relative refractive index difference delta ₄ with respect to the cladding of said fourth segment is more preferable to be 0.03% or less than 0.01%.

  By having such a refractive index distribution, even when the ratio between the core diameter and the cladding diameter changes, the change in bending loss of light propagating through the core can be further suppressed.

As described above, according to the present invention, there is provided a dispersion-shifted optical fiber that can suppress the bending loss of propagating light even when the refractive index of the cladding varies due to manufacturing.
Is provided.

It is a figure which shows the structure of a cross section perpendicular | vertical to the longitudinal direction of the dispersion shift optical fiber which concerns on 1st Embodiment of this invention. It is a figure which shows the relative refractive index distribution with respect to the clad of the dispersion shift optical fiber of FIG. It is a figure which shows the mode of the dispersion shift optical fiber which concerns on 2nd Embodiment of this invention. It is a figure which shows the relative refractive index distribution with respect to the clad of the dispersion shift optical fiber of FIG.

  Hereinafter, preferred embodiments of a dispersion-shifted optical fiber according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a cross-sectional structure perpendicular to the longitudinal direction of a dispersion-shifted optical fiber according to this embodiment.

The dispersion-shifted optical fiber DSF1 of this embodiment has a dispersion value of 2.0 ps / nm / km or more and 13.5 ps / nm / km or less of light having a wavelength of 1530 nm to 1625 nm, and a dispersion slope of light having a wavelength of 1550 nm. There is a 0.092ps / ^nm 2 / km or less, the cable cutoff wavelength is less 1450 nm, the effective core area in the light of the wavelength of 1550nm is at 65 .mu.m ² or more 90 [mu] m ² or less, the mode of light having a wavelength of 1550nm The field diameter is set to 9.2 μm or more and 10.5 μm or less. That is, the dispersion-shifted optical fiber DSF1 is a dispersion-shifted optical fiber that propagates C-band and L-band light.

  As shown in FIG. 1, the dispersion-shifted optical fiber DSF1 of this embodiment includes a core 1 and a clad 2 that surrounds the outer peripheral surface of the core 1 without a gap.

  The core 1 includes a first segment 11, a second segment 12 surrounding the outer peripheral surface of the first segment 11 without a gap, a third segment 13 surrounding the outer peripheral surface of the second segment 12 without a gap, and an outer periphery of the third segment 13. And a fourth segment 14 surrounding the surface without a gap. Moreover, the 1st segment 11 contains the 1st center segment 10 containing the center axis | shaft of the core 1, as shown with a broken line in FIG. Thus, the dispersion-shifted optical fiber DSF1 of this embodiment has 4 segments.

The radius r ₀ of the first central segment 10 is 0.5 μm or more and 2.8 μm or less. The radius r ₁ of the first segment 11 is 1.8 μm or more and 4.5 μm or less. The radius r ₂ of the second segment 12 is 4.0 μm or more and 8.0 μm or less. The radius r ₃ of the third segment 13 is 4.5 μm or more and 8.5 μm or less. The radius r ₄ of the fourth segment 14 is set to 8.0 μm or more and 16.0 μm or less. In addition, the radius of each segment refers to the radius of the outer peripheral surface of each segment.

Further, the radius _{r 0} of the first central segment 10, the radius _{r 1} of the first segment 11, the radius _{r 2} of the second segment 12, the radius _{r 3} of the third segment 13, the radius r of the fourth segment 14 _{Between 4} ,
r ₀ <r ₁ <r ₂ <r ₃ <r ₄
Is established.

FIG. 2 is a diagram showing a distribution of relative refractive index differences with respect to the cladding 2 in the radial direction of the dispersion shifted optical fiber DSF1 shown in FIG. However, FIG. 2 shows a state of the refractive index distribution only on one side in the radial direction from the central axis of the dispersion shifted optical fiber DSF1. The relative refractive index difference Δ _{0 with} respect to the clad 2 of the first central segment 10 is set to 0.4% or more and 0.9% or less. The relative refractive index difference Δ ₂ of the second segment 12 with respect to the cladding 2 is set to be 0.00% or more and 0.07% or less. As described above, the relative refractive index difference Δ ₂ of the second segment 12 with respect to the cladding 2 is smaller than the relative refractive index difference Δ ₀ of the first central segment 10 with respect to the cladding 2. The relative refractive index difference with respect to the cladding 2 decreases from the outer periphery to the inner periphery of the second segment 12. The relative refractive index difference Δ ₃ of the third segment 13 with respect to the cladding 2 is set to be 0.285% or more and 0.5% or less. The relative refractive index difference delta ₄ with respect to the cladding 2 of the fourth segment 14 is 0.04% or less than 0.005%.

The materials constituting the core 1 and the cladding 2 of the dispersion shifted optical fiber DSF1 are as follows. For example, the cladding 2 is made of pure quartz, the first segment 11 and the third segment 13 of the core 1 are made of quartz to which a dopant for increasing the refractive index is added, and the second segment 12 and the fourth segment 14 are Further, it is composed of quartz to which a dopant for increasing the refractive index and a dopant for decreasing the refractive index are appropriately added. Germanium (Ge) can be cited as a representative example of the dopant having the function of increasing the refractive index. Germanium is added as GeO _2. Further, fluorine (F) can be typically given as a dopant having an action of decreasing the refractive index. The dopant added to each segment of the core 1 is at least one selected from germanium, aluminum (Al), phosphorus (P), and fluorine, or two or more, and the relative refractive index difference with respect to the clad 2 is as described above. The type and amount of addition are appropriately selected so as to be in the range.

  Each segment of the core 1 has the above-described radius and relative refractive index difference with respect to the cladding 2, so that the dispersion-shifted optical fiber DSF1 has the above-described dispersion value, dispersion slope, cable cutoff wavelength, effective core area, mode Has a field diameter.

  As described above, the dispersion-shifted optical fiber DSF1 of the present embodiment has the core 1 diameter (core diameter) and the clad 2 as each segment of the core 1 has a relative refractive index difference with respect to the radius and the clad 2 described above. Even when the ratio to the diameter (cladding diameter) changes, the bending loss of light propagating through the core 1 can be suppressed from changing.

Note that, as described above, the dispersion-shifted optical fiber DSF1 has r ₀ <r _1, and the first segment 11 has a relative refractive index difference with respect to the cladding 2 from the outer periphery of the first center segment 10 to the inner periphery of the second segment 12. Decreases. Therefore, when r ₀ <r ₁ , the shape of the refractive index distribution of the first segment 11 is approximately trapezoidal.

  Thus, when the shape of the refractive index distribution of the first segment 11 is substantially trapezoidal, it is preferable that each segment has a radius and a relative refractive index difference with respect to the cladding 2 within the following ranges.

That is, the radius r ₀ of the first central segment 10 is set to 0.5 μm or more and 1.3 μm or less, the radius r ₁ of the first segment 11 is set to 2.0 μm or more and 4.5 μm or less, and the radius r of the second segment 12 is set. ₂ is 5.0 μm or more and 8.0 μm or less, the radius r ₃ of the third segment 13 is 6.0 μm or more and 8.5 μm or less, and the radius r ₄ of the fourth segment 14 is 9.0 μm or more and 16.0 μm or less. It is said. However, r ₁ <r ₂ <r ₃ <r ₄ is satisfied as described above.

Further, the relative refractive index difference Δ _{0 of} the first central segment 10 with respect to the cladding 2 is set to 0.5% or more and 0.9% or less, and the relative refractive index difference Δ _{2 of} the second segment 12 with respect to the cladding ₂ is 0.00%. above is 0.07% or less, the cladding 2 with respect to the relative refractive index difference delta ₃ of the third segment 13 is 0.5% or less than 0.285%, the relative refractive index difference with respect to the cladding 2 of the fourth segment 14 delta ₄ is 0.005% or more and 0.04% or less.

  When the first segment 11 has a substantially trapezoidal refractive index profile, each segment of the core 1 has a relative refractive index difference with respect to the radius and the cladding 2 described above. It is possible to gradually change the viscosity difference in the region from the outer periphery of 10 to the second segment 12. For this reason, a large residual stress can be reduced and an increase in transmission loss can be suppressed.

  As described above, when the shape of the refractive index distribution of the first segment 11 is substantially trapezoidal, it is more preferable that each segment has a radius and a relative refractive index difference with respect to the cladding 2 within the following ranges.

That is, the radius r ₀ of the first center segment 10 is set to 0.5 μm or more and 1.0 μm or less, the radius r ₁ of the first segment 11 is set to 3.0 μm or more and 4.5 μm or less, and the radius r of the second segment 12 is set. ₂ is 5.2 μm or more and 6.5 μm or less, the radius r ₃ of the third segment 13 is 6.5 μm or more and 8.0 μm or less, and the radius r ₄ of the fourth segment 14 is 10.0 μm or more and 13.5 μm or less. It is said. However, r ₁ <r ₂ <r ₃ <r ₄ is satisfied as described above.

Further, the relative refractive index difference Δ _{0 of} the first center segment 10 with respect to the cladding 2 is set to 0.6% or more and 0.8% or less, and the relative refractive index difference Δ _{2 of} the second segment 12 with respect to the cladding ₂ is 0.02%. The relative refractive index difference Δ _{3 of} the third segment 13 relative to the cladding 2 is set to 0.285% or higher and 0.4% or lower, and the relative refractive index difference Δ of the fourth segment 14 relative to the cladding 2 is set to 0.065% or less. ₄ is 0.01% or more and 0.03% or less.

  Even if the ratio between the diameter of the core 1 and the diameter of the clad 2 changes because each segment of the core 1 has the above-described radius and the relative refractive index difference with respect to the clad 2, the light propagating through the core 1 The bending loss can be further suppressed.

(Second Embodiment)
Next, a second embodiment of the dispersion-shifted optical fiber according to the present invention will be described in detail with reference to FIGS. Note that the same or equivalent components of the dispersion-shifted optical fiber DSF1 of the first embodiment are denoted by the same reference numerals unless otherwise described, and redundant description is omitted.

  FIG. 3 is a diagram showing a cross-sectional structure perpendicular to the longitudinal direction of the dispersion-shifted optical fiber according to the present embodiment.

Also in this embodiment, the dispersion-shifted optical fiber DSF2 has a dispersion value of 2.0 ps / nm / km or more and 13.5 ps / nm / km or less in light having a wavelength of 1530 nm or more and 1625 nm or less, and in light having a wavelength of 1550 nm. dispersion slope is at 0.092ps / ^nm 2 / km or less, the cable cutoff wavelength is less 1450 nm, the effective core area in the light of the wavelength of 1550nm is at 65 .mu.m ² or more 90 [mu] m ² or less, the wavelength of 1550nm light The mode field diameter at 9.2 is not less than 9.2 μm and not more than 10.5 μm. That is, the dispersion-shifted optical fiber DSF2 is a dispersion-shifted optical fiber that propagates C-band and L-band light, like the dispersion-shifted optical fiber DSF1 of the first embodiment.

The dispersion shifted optical fiber DSF2 of the present embodiment has four segments, but differs from the dispersion shifted optical fiber DSF1 of the first embodiment in that r ₀ = r ₁ .

The dispersion-shifted optical fiber of this embodiment, the radius _{r 0} of the first central segment 10, and the radius _{r 1} is equal to 1.8μm or 2.8μm or less to each other of the first segment 11.

4 is a diagram showing the relative refractive index distribution of the dispersion-shifted optical fiber DSF2 in FIG. 3 by the same method as in FIG. Also in the present embodiment, as in the first embodiment, in the first segment 11, the relative refractive index difference with respect to the cladding 2 decreases from the outer periphery of the first center segment 10 to the inner periphery of the second segment 12. However, as shown in FIG. 4, in this embodiment, r ₀ = r ₁ , so that the outer periphery of the first center segment 10 and the inner periphery of the second segment 12 (the outer periphery of the first segment 11) are equal. As shown in FIG. 4, the shape of the refractive index distribution of the first segment 11 is generally a step type.

  As described above, when the shape of the refractive index distribution of the first segment 11 is substantially a step, it is preferable that each segment has a radius and a relative refractive index difference with respect to the cladding 2 within the following ranges.

That is, the radius r ₀ of the first central segment 10 (the radius r ₁ of the first segment 11) is 1.8 μm or more and 2.8 μm or less, and the radius r ₂ of the second segment 12 is 5.0 μm or more and 6.6 μm or less. The radius r ₃ of the third segment 13 is set to 6.1 μm or more and 8.5 μm or less, and the radius r ₄ of the fourth segment 14 is set to 8.0 μm or more and 16.0 μm or less. However, as described above, r ₀ (r ₁ ) <r ₂ <r ₃ <r ₄ holds.

Further, the relative refractive index difference Δ _{0 of} the first central segment 10 with respect to the cladding 2 (the relative refractive index difference Δ _{1 of} the first segment 11 with respect to the cladding 2) is set to 0.4% or more and 0.8% or less, and the second segment the relative refractive index difference delta ₂ with respect to the cladding 2 of 12 is 0.06% or less than 0.00%, the third cladding 2 with respect to the relative refractive index difference delta ₃ segments 13 0.5% inclusive 0.285% is a, fourth segment 14 cladding 2 with respect to the relative refractive index difference delta ₄ of is 0.04% or less than 0.005%.

  When the first segment has a substantially trapezoidal refractive index profile, the refractive index is changed in the first segment 11 by making each segment of the core 1 have a relative refractive index difference with respect to the radius and the cladding 2 described above. Manufacturing is easier than in the case of making them.

  As described above, when the shape of the refractive index distribution of the first segment 11 is generally a step, it is more preferable that each segment has a radius and a relative refractive index difference with respect to the cladding 2 within the following ranges.

That is, the radius r ₀ of the first center segment 10 (radius r ₁ of the first segment 11) is 2.0 μm or more and 2.6 μm or less, and the radius r ₂ of the second segment 12 is 5.0 μm or more and 6.0 μm or less. The radius r ₃ of the third segment 13 is set to 6.1 μm or more and 7.5 μm or less, and the radius r ₄ of the fourth segment 14 is set to 11.0 μm or more and 15.0 μm or less. However, r ₁ (r ₁ ) <r ₂ <r ₃ <r ₄ is established as described above.

Further, the relative refractive index difference Δ ₀ (relative refractive index difference Δ ₁ ) of the first center segment 10 with respect to the cladding 2 is set to 0.47% or more and 0.67% or less, and the second segment the relative refractive index difference delta ₂ with respect to the cladding 2 of 12 is 0.06% or less than 0.02%, the third cladding 2 with respect to the relative refractive index difference delta ₃ segments 13 or less 0.35% or more 0.285% is a, fourth segment 14 cladding 2 with respect to the relative refractive index difference delta ₄ of is 0.025% or less than 0.010%.

  Even if the ratio between the diameter of the core 1 and the diameter of the clad 2 changes because each segment of the core 1 has the above-described radius and the relative refractive index difference with respect to the clad 2, the light propagating through the core 1 The bending loss can be further suppressed.

  The present invention has been described above by taking the first and second embodiments as examples, but the present invention is not limited to these.

  For example, in the first embodiment, in the first segment 11, the relative refractive index with respect to the cladding 2 decreases in an inclined manner from the outer peripheral surface of the first center segment 10 to the inner periphery of the second segment 12. However, in the present invention, in the first segment 11, it is sufficient that the relative refractive index with respect to the cladding 2 decreases from the outer peripheral surface of the first center segment 10 to the inner periphery of the second segment 12, and the first segment 11 is lowered stepwise. Also good.

  Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
A simulation was performed using the dispersion-shifted optical fiber DSF1 shown in FIGS. 1 and 2 as a model. Radius _{r 0} of the first central segment 10 of the first segment 11, the radius _{r 1} of the first segment 11, the radius _{r 2} of the second segment 12, the radius _{r 3} of the third segment 13, the radius _{r 4} of the fourth segment 14 Was as shown in Table 1 below. Also, the relative refractive index difference delta ₀ with respect to the cladding 2 of the first central segment _10, the relative refractive index difference with respect to the cladding 2 of the second segment 12 delta _2, the relative refractive index difference with respect to the cladding 2 of the third segment 13 delta _3, fourth The relative refractive index difference Δ ₄ with respect to the clad 2 of the segment 14 is as shown in Table 1 below, and the relative refractive index difference with respect to the clad 2 from the outer peripheral surface of the first center segment 10 to the inner periphery of the second segment 12 in the first segment 11. Was assumed to fall in an inclined manner.

  Further, the cut-off wavelength (λc) of the dispersion-shifted optical fiber DSF1 and the effective core cross-sectional area (Aeff) when light having a wavelength of 1550 nm is propagated as described above are the radius of each segment and the relative refractive index difference with respect to the cladding 2. A mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, a dispersion value (Disp) of light having a wavelength of 1550 nm, a dispersion slope (Slope) of light having a wavelength of 1550 μm, and a dispersion-shifted optical fiber DSF1 bent to a diameter of 20 mm Table 2 shows the bending loss (Bloss) of light having a wavelength of 1550 nm propagating and the loss (Loss) of light having a wavelength of 1550 nm propagating through the linear dispersion-shifted optical fiber DSF1.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Examples 2 to 11)
Table 1 shows the radius (r ₀ , r ₁ , r ₂ , r ₃ , r ₄ ) of each segment and the relative refractive index difference (Δ ₀ , Δ ₂ , Δ ₃ , Δ ₄ ) with respect to the cladding 2. The dispersion shifted optical fiber DSF1 was simulated in the same manner as in Example 1 except for the above.

  The cutoff wavelength (λc) of the dispersion shifted optical fiber DSF1 in this case, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength Dispersion value (Disp) of light at 1550 nm, dispersion slope (Slope) of light at wavelength 1550 μm, bending loss (Bloss) of light at wavelength 1550 nm propagating through dispersion shifted optical fiber DSF 1 bent to a diameter of 20 mm, linear dispersion shift Table 2 shows the loss (loss) of light having a wavelength of 1550 nm propagating through the optical fiber DSF1.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Example 12)
Simulation was performed using the dispersion-shifted optical fiber DSF2 shown in FIGS. 3 and 4 as a model. Accordingly, a first central segment 10 radius _{r 0} is the radius _{r 1} of the first segment 11 are equal to each other. Radius _{r 0} of the first central segment 10 of the first segment 11 (the radius _r 1 of the first segment 11), the radius _{r 2} of the second segment 12, the radius _{r 3} of the third segment 13, the radius r of the fourth segment 14 ₄ was as shown in Table 1 below. Also, the relative refractive index difference delta ₀ with respect to the cladding 2 of the first central segment _10, the relative refractive index difference with respect to the cladding 2 of the second segment 12 delta _2, the relative refractive index difference with respect to the cladding 2 of the third segment 13 delta _3, fourth the relative refractive index difference delta ₄ with respect to the cladding 2 of the segment 14 was set as shown in the following table 1.

  Further, the cut-off wavelength (λc) of the dispersion-shifted optical fiber DSF2 that is the radius of each segment and the relative refractive index difference with respect to the cladding 2, and the effective core area (Aeff) when light having a wavelength of 1550 nm propagates. A mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, a dispersion value (Disp) of light having a wavelength of 1550 nm, a dispersion slope (Slope) of light having a wavelength of 1550 μm, and a dispersion-shifted optical fiber DSF2 bent to a diameter of 20 mm Table 2 shows the bending loss (Bloss) of light having a wavelength of 1550 nm propagating and the loss (Loss) of light having a wavelength of 1550 nm propagating through the linear dispersion-shifted optical fiber DSF2.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Examples 13 to 18)
Table 1 shows the radius (r ₀ (r ₁ ), r ₂ , r ₃ , r ₄ ) and the relative refractive index difference (Δ ₀ (Δ ₁ ), Δ ₂ , Δ ₃ , Δ ₄ ) of each segment. A simulation of the dispersion-shifted optical fiber DSF2 was performed in the same manner as in Example 4 except that.

  In this case, the cutoff wavelength (λc) of the dispersion-shifted optical fiber DSF2, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength Dispersion value (Disp) of light of 1550 nm, dispersion slope (Slope) of light of wavelength 1550 μm, bending loss (Bloss) of light of wavelength 1550 nm propagating through dispersion shifted optical fiber DSF 2 bent to a diameter of 20 mm, linear dispersion shift Table 2 shows the loss (loss) of light having a wavelength of 1550 nm propagating through the optical fiber DSF2.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Comparative Example 1)
As the three-segment dispersion-shifted optical fiber obtained by removing the fourth segment 14 from the dispersion-shifted optical fiber DSF1 shown in FIGS. 1 and 2, the radius (r ₀ , r ₁ , r ₂ , r ₃ ) of each segment and A dispersion-shifted optical fiber was simulated in the same manner as in Example 1 except that the relative refractive index differences (Δ ₀ , Δ ₂ , Δ ₃ ) with respect to the clad 2 were as shown in Table 1.

  In this case, the cutoff wavelength (λc) of the dispersion-shifted optical fiber, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength of 1550 nm Dispersion value (Disp) of light, dispersion slope (Slope) of light having a wavelength of 1550 μm, bending loss (Bloss) of light of wavelength 1550 nm propagating through a dispersion-shifted optical fiber bent to a diameter of 20 mm, linear dispersion-shifted optical fiber Table 2 shows the loss (Loss) of light having a wavelength of 1550 nm propagating through the light.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Comparative Example 2)
As the three-segment dispersion-shifted optical fiber obtained by removing the fourth segment 14 from the dispersion-shifted optical fiber DSF2 shown in FIGS. 3 and 4, the radius (r ₀ , r ₁ , r ₂ , r ₃ ) of each segment and A dispersion-shifted optical fiber was simulated in the same manner as in Example 4 except that the relative refractive index differences (Δ ₀ , Δ ₂ , Δ ₃ ) with respect to the clad 2 were as shown in Table 1.

  In this case, the cutoff wavelength (λc) of the dispersion-shifted optical fiber, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength of 1550 nm Dispersion value (Disp) of light, dispersion slope (Slope) of light having a wavelength of 1550 μm, bending loss (Bloss) of light of wavelength 1550 nm propagating through a dispersion-shifted optical fiber bent to a diameter of 20 mm, linear dispersion-shifted optical fiber Table 2 shows the loss (Loss) of light having a wavelength of 1550 nm propagating through the light.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Comparative Example 3)
Table 1 shows the radius (r ₀ , r ₁ , r ₂ , r ₃ , r ₄ ) of each segment and the relative refractive index difference (Δ ₀ , Δ ₂ , Δ ₃ , Δ ₄ ) with respect to the cladding 2. The dispersion shifted optical fiber DSF1 was simulated in the same manner as in Example 1 except for the above.

  The cutoff wavelength (λc) of the dispersion shifted optical fiber DSF1 in this case, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength Dispersion value (Disp) of light at 1550 nm, dispersion slope (Slope) of light at wavelength 1550 μm, bending loss (Bloss) of light at wavelength 1550 nm propagating through dispersion shifted optical fiber DSF 1 bent to a diameter of 20 mm, linear dispersion shift Table 2 shows the loss (loss) of light having a wavelength of 1550 nm propagating through the optical fiber DSF1.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

(Comparative Examples 4-6)
Table 1 shows the radius (r ₀ (r ₁ ), r ₂ , r ₃ , r ₄ ) and the relative refractive index difference (Δ ₀ (Δ ₁ ), Δ ₂ , Δ ₃ , Δ ₄ ) of each segment. A simulation of the dispersion-shifted optical fiber DSF2 was performed in the same manner as in Example 4 except that.

  In this case, the cutoff wavelength (λc) of the dispersion-shifted optical fiber DSF2, the effective core area (Aeff) when light having a wavelength of 1550 nm propagates, the mode field diameter (MFD) when light having a wavelength of 1550 nm propagates, and the wavelength Dispersion value (Disp) of light of 1550 nm, dispersion slope (Slope) of light of wavelength 1550 μm, bending loss (Bloss) of light of wavelength 1550 nm propagating through dispersion shifted optical fiber DSF 2 bent to a diameter of 20 mm, linear dispersion shift Table 2 shows the loss (loss) of light having a wavelength of 1550 nm propagating through the optical fiber DSF2.

  Further, when the ratio of the diameter of the core 1 to the diameter of the clad 2 fluctuates by 1%, the bending loss fluctuation rate (Bloss VR) is as shown in Table 2.

Tables 1 and 2 are shown below. In Table 1 below, the shape of the refractive index distribution of the first segment 11 is described.

  Table 2 shows that according to the dispersion-shifted optical fibers of Examples 1 to 18 of the present invention, the change in bending loss is suppressed even when the ratio of the core diameter to the cladding diameter changes. . Therefore, according to the dispersion-shifted optical fiber of the present invention, it was shown that even when the diameter of the clad glass body of the optical fiber preform varies due to manufacturing, the bending loss of the propagating light can be suppressed. .

  In particular, in the dispersion shifted fibers of Examples 7 to 11 among Examples 1 to 11 in which the shape of the refractive index distribution of the first segment 11 is trapezoidal, the ratio between the diameter of the core 1 and the diameter of the cladding 2 is high. A favorable result was obtained in which the rate of change in bending loss (Bloss VR) when it fluctuates by 1% can be suppressed to less than 4%. Further, in the dispersion shifted fibers of Examples 15 to 16 among Examples 12 to 18 in which the shape of the refractive index distribution of the first segment 11 is a step type, the ratio between the diameter of the core 1 and the diameter of the cladding 2 is A favorable result was obtained in which the rate of change in bending loss (Bloss VR) when it fluctuates by 1% can be suppressed to less than 4%.

  As described above, according to the dispersion-shifted fiber of the present invention, even when the ratio of the core diameter to the cladding diameter varies, it is possible to suppress a change in the bending loss of the propagating light. It can be used in the field of communications.

DSF1, DSF2 ... dispersion shifted optical fiber 1 ... core 2 ... cladding 10 ... first central segment 11 ... first segment 12 ... second segment 13 ... third segment 14 ... Fourth segment

Claims (5)

The dispersion value in the light with a wavelength of 1530 nm or more and 1625 nm or less is 2.0 ps / nm / km or more and 13.5 ps / nm / km or less, and the dispersion slope in the light with a wavelength of 1550 nm is 0.092 ps / nm ² / km or less. There, the cable cutoff wavelength is less than or equal 1450 nm, the effective core area in the light of the wavelength of 1550nm is at 65 .mu.m ² or more 90 [mu] m ² or less, the mode field diameter of more than 9.2μm in the light of the wavelength of 1550nm 10.5 [mu] m or less A dispersion-shifted optical fiber,
A core including a first segment including a central axis of the core; a second segment surrounding the outer peripheral surface of the first segment without gap; a third segment surrounding the outer peripheral surface of the second segment without gap; and the third segment Having a fourth segment surrounding the outer peripheral surface of the segment without gaps,
The first segment includes a first central segment including the central axis;
The radius r ₀ of the first central segment is 0.5 μm or more and 2.8 μm or less, the radius r ₁ of the first segment is 1.8 μm or more and 4.5 μm or less, and the radius r ₂ of the second segment is 4.0 μm or more and 8.0 μm or less, the radius r ₃ of the third segment is 4.5 μm or more and 8.5 μm or less, and the radius r ₄ of the fourth segment is 8.0 μm or more and 16.0 μm or less. And r ₀ ≦ r ₁ <r ₂ <r ₃ <r ₄ holds,
The relative refractive index difference Δ _{0 with} respect to the cladding surrounding the core of the first central segment is 0.4% or more and 0.9% or less, and the relative refractive index difference Δ _{2 with} respect to the cladding of the second segment is 0.00. % is 0.07% or less, the third segment relative refractive index difference delta ₃ with respect to the cladding of the 0.5% or less than 0.285%, the relative refractive index difference with respect to the cladding of the fourth segment delta ₄ is 0.04% or less than 0.005%, wherein the relative refractive index difference with respect to the cladding toward the inner periphery of the second segment from the outer periphery of said first central segment in the first segment is reduced Dispersion shifted optical fiber. The radius r ₀ of the first center segment is 1.8 μm or more, the radius r ₁ of the first segment is 2.8 μm or less, the radius r ₀ of the first center segment and the radius r of the first segment ₁ , the radius r ₂ of the second segment is 5.0 μm or more and 6.6 μm or less, the radius r ₃ of the third segment is 6.1 μm or more,
The relative refractive index difference delta ₀ for the cladding of the first central segment is a 0.8% or less, characterized in that the relative refractive index difference delta ₂ with respect to the cladding of the second segment is less 0.06% The dispersion-shifted optical fiber according to claim 1. The radius r ₀ of the first central segment is 2.0 μm or more and 2.6 μm or less, the radius r ₂ of the second segment is 6.0 μm or less, and the radius r ₃ of the third segment is 7.5 μm or less. The radius r ₄ of the fourth segment is 11.0 μm or more and 15.0 μm or less,
The relative refractive index difference Δ ₀ of the first central segment with respect to the cladding is 0.47% or more and 0.67% or less, and the relative refractive index difference Δ ₂ of the second segment with respect to the cladding is 0.02% or more. is, the third segment relative refractive index difference delta ₃ with respect to the cladding of the set to 0.35% or less, the fourth segment the relative refractive index difference delta ₄ and the cladding is 0.025% or less than 0.010% of The dispersion-shifted optical fiber according to claim 2, wherein The radius r ₀ of the first central segment is smaller than the radius r ₁ of the first segment;
The radius r ₀ of the first central segment is 1.3 μm or less, the radius r ₁ of the first segment is 2.0 μm or more, the radius r ₂ of the second segment is 5.0 μm or more, The radius r ₃ of the third segment is 6.0 μm or more, the radius r ₄ of the fourth segment is 9.0 μm or more, and the relative refractive index difference Δ ₀ of the first central segment with respect to the cladding is 0.5%. The dispersion-shifted optical fiber according to claim 1, wherein the dispersion-shifted optical fiber is as described above. The radius r ₀ of the first central segment is 0.5 μm to 1.0 μm, the radius r ₁ of the first segment is 3.0 μm to 4.5 μm, and the radius r ₂ of the second segment is The radius r ₃ of the third segment is 6.5 μm or more and 8.0 μm or less, and the radius r ₄ of the fourth segment is 10.0 μm or more and 13.5 μm or less. ,
The relative refractive index difference Δ ₀ of the first central segment with respect to the cladding surrounding the core is 0.6% or more and 0.8% or less, and the relative refractive index difference Δ ₂ of the second segment with respect to the cladding is 0.020. % is a more 0.065% or less, the third segment relative refractive index difference delta ₃ with respect to the cladding is 0.4% or less, the relative refractive index difference delta ₄ with respect to the cladding of said fourth segment is 0. The dispersion-shifted optical fiber according to claim 4, wherein the dispersion-shifted optical fiber is 01% or more and 0.03% or less.

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